Method of producing vitreous enamelled metal articles



Patented Sept. 9, 1952 METHOD OF PRODUCING VITREOUS I ENAMELLED METALARTICLES Roland Aiwhitbeck, Lorain, Ohio, assignor .to f

Gilron Products Company,

corporation of Qliio Cleveland, Ohio, a

No Drawing, Application October is, 1949, r

- Serial No. 122,147

This invention relates to a method'iof producing vitreous enamelledmetal products. a

In the prior method .of vitreous enamelling in general use today, thesteel enamelling stock used is of a type 1 having a rough surfacefandgreater porosity-than steels of likecomposition produced for other uses,Thesurface generally is a series of substantial Jpeaks anddepressions,providing what is generally referred to as a coarse or heavy"tooth., 1 v

The prior method of forming vitreous enamelling stock has maydisadvantages, one of the most important beihgfthatl in the rolling,'forming and fabricating operations the tooth or the metal is levelledofifand reducedand the pores become filled with the lubricating oils,greases and compounds'lso that thefjOVerall. pcrosity of the metal alsois reduced. e a

As a result, the oils and greases must beremoved from the metal and themetal pickled to restore the tooth and the porosity.

Furthermore, in the prior processes, thelu bricants containingoils,greases, and fatty acids must besaponified and emulsified for removal.If not removed, they are detrimental to enamelling. In fact, if theyremain long on the material, they etch and oxidize the surface to suchan extent that the stock requires pickling and neutralizing torec'ondition it for enamelling.

Furthermore, the 011s; greases and fatty acids the adhesion of theenameL' Most rejects in' "-14. Claims. (01. 29-148) prior enamellingprocesses are-due to these 1u-" bricants becomingentrapped in the metalprior to enamelling.

Vitreous enamel stock is received from the mill in clean condition.Starting vvith'such clean, relatively'porous and heavy toothed'stock,the prior method of vitreousenamelling, or orform ing articles forvitreous enamelling, comprises generally the following steps, in order:first, the clean stock is oiled-and blanked out cold; next, it is coatedwith lubricating'oil or greases and drawn or o rwise formed to shape andfabri-li' cated; then it is cleaned by boiling in a strong alkalinesolution following which it is rinsed with water; after rinsing, it issubjected to a,

deep picklestep torestore the tooth of the metal.

which hasbeen badlysmashed down during the forming operations. Afterbeing deep pickled-it is water rinsed and passed through av neutralizingbath, dried and then enamelled, the enamelling steps following theconventional procedure. As an example of the time cycle required, agiven piece. may be processed, beginning with the initial oiling forblanking and continuing through ,final drying preparatory to ,enamell-ing, in thirty-five minutes. Of this time, about'thirty minutes isrequired for the deep pickling 'opera,-

tion to restore the tooth which was. damaged during forming. I v

In accordance with my invention the-original tooth and porosity ofv thestock are-preserved in substantially their original. condition. I My newprocess comprises coating clean vitreous enamel, stock with a watersoluble, self-adherent, dry,.

homogeneous, protective, lubricating and reinforcing coating sothatithevalleys between the.

so-called teeth of the stock are well filledand the teeth themselvescoated over, blanking the coated stock, if blanking is, required, in theabsence of any additional lubricants, forming the stock in the conditionin which it exists after blanking, or if blanking is not required, inthe condition in which it exists after originally coating, washing offthe stockwith water, and. then drying and vitreous enamelling theformed.

stock with the tooth thereof substantially in the shape in which itexisted at the completion of the washing step. I

If desired, in order to assure the optimum results and eliminate anytroubles due to possible extraneous circumstances, such as slightcontamination of thebath or stock from greases upon. withdrawaltherefrom.

The term aqueous bath as used'in the claims is meant to include wateralone as well as alkaline cleaning solutions and other aqueous cleaningsolutions.

Another optional step following the cleaning in water, or in the aqueouscleaning'bath, is to subject the sheet to a light pickle forsuperficially .roughening the surface of the stock without substantiallyaffecting the shape of the tooth which latter, after the formingoperation, is in substantially the condition it was in prior to forming.If the light pickle step is used, the stock is passed promptlythereafter through a neutralizing bath to eliminate from the stock anypossible acids from the pickling bath. In fact, whether the light picklestep is used or not, the neutralizing step is desirable because itoccasionally happens that there is some carryover of residual acids fromthe pickling steps performed at the steel mill in originally producingthe vitreous enamelling stock.

As a comparative example of the time cycle required in my process, if itis assumed that the same piece heretofore mentioned in describing thetime cycle of the prior process were processed in accordance with myinvention, starting with the clean stock, coating, blanking, forming,washing with a mild aqueous alkaline cleaner, cold rinsing, lightpickling, neutralizing and drying, the entire time required is aboutfive minutes as compared to the thirty-five minutes required in theprior process, the light pickling step in my process requiring about oneminute.

Thus I have found that by properly .filling the valleys between theteeth and coating the teeth of the stock with an easily removedlubricating and reinforcing material which is water soluble and, whendried on the stock, produces a dry, solid, permanent, self-adherent,homogeneous, lubricating and protective film which has substantial bodyresistance to compression, the tooth of the metal can be laterallysupported to an extent that it effectively resists the reduction andleveling off effect occasioned by the'forming and fabricating'operationsso that, upon removal of the material after formation, the tooth andsurface of the formed and fabricated stock are so nearly in theiroriginal condition that the stock is. suitable without the heretoforerequired deep pickling step or other steps heretofore required forvitreous enamelling.

Further, I have found that by selecting such a material which also fillsor seals the pores of the metal yet is easily removed without chemicalaction on the metal itself, the porosity of the metal, after forming andfabricating, can be maintained substantially inits original condition.

According to my present invention, the raw,

ars t p ous steel enamelli'ng stock is coated with a homogeneous,completely water soluble material. This coating may be applied to theraw metal while it is in the condition in which it issues from the steelmill. However, if any oils, greases, rust proofing materials and thelike have been placed on the material, at the mill or in subsequenthandling prior to the coating step of the present invention, the metalis thoroughly cleaned so as to restore its surface as near to theoriginal milled condition as possible.

A suitable coating composition for this process comprises lubricatingand protective organic binder and water soluble alkaline earth metalborates, such composition being free from any inorganic barriermaterial.

The proportions of the ingredients of the dry mix composition for use inmy process are as follows, the percentage given being by weight:

The coating is applied by dissolving the composition in water in theratio of about one pound of dry mix to one gallon of water and isapplied to the stock by dipping or otherwise, followed by drying, andthereby forms on the stock a dry, homogeneous, self-adherent film whichis both lubricating and protective.

One class of materials which may be used as the organic lubricatingbinders are water-soluble soaps, preferably having a melting point of atleast about 3.6 C. upwardly and more particularly high titre soapshaving a melting point of from between about 36 to 42 C. and up,specific examples being tallow soap, palm oil soap stearic acid soap,cocoa butter soap, Borneo tallow soap, hydrogenated tallow soap,coaceric soap, Japanic soap, palmitic acid soap, stearin flux soap,multiple pressed tallow soap, hydrogenated palm oil soap, andmultiple-pressed palm oil soap. It should be noted that each of theabove soaps may be used individually or in admixture with one or more ofthe other soaps in any desired proportions, in so long as the amount ofsoap-present is within the broad limits hereinbefore recited. 7

An additional class of materials are watersoluble aliphatic polyhydricalcohols having less than four hydroxy groups, fatty acid esters thereofor mixtures of either or both, and with a particular preference forthose having a melting point of at least about 40 C., specific examplesbeing polyethylene glycol, polyethylene glycol oleate, glycerylstearate, propylene glycol sterate, di-glycol stearate, etc.

As herein'before indicated, mixtures of compounds in each class arecontemplated for use in blending the ultimate compositoin; More over, itshould be particularly stated thata mixture of the two aforementionedclasses may be employed, such as, for example, a soap and a polyhydricalcohol, soap and an ester of the alcohol, a mixture of soaps and analcohol or an ester or .a mixture of the two. When employing such amixture the soap preferably should be in the same or greater amount asthe polyhydric alcohol.

The alkali metal borates employed in combination with the organiclubricating binder include borax, lithium borate, and potassium borate.Borax is the preferred material due to its ready availability and lowcost and also, in certain methods of application, the other borates tendto disburse the organic binder and if the coated metal stock stands forany considerable period of time it tends to become tacky.

In some instances, it will be found beneficial to combine with theaforesaid composition a minor amount of an organic hydrophilliccolloidal material such as, for example, cornstarch, potato starch,wheat starch, etc. Under such circumstances, the colloidal material willbe present in an amount from between about 1% to 8%, the lubricatingbinder about 15 to 25% and the borate about 67 to 84%.

After forming, the article is Washed in water in any conventionalwashing machine and then dried. It will be found that the water solublecoating is completely removed from the valleys between the projectionsor teeth of the metal and from the pores by the water cleaningoperation, and that neither the tooth nor porosity has been adverselyafiected substantially by the cold forming and fabrication operations.Accordingly, without any further steps, the dried article is thenenamelled in the usual manner of enamelling flat raw enamel stock havingits original heavily toothed and porous surface.

It must be understood, however, thatif there is to be an appreciabletime delay between the step of water washing and enamelling, it isdesirable to protect the surface of the article temporarily from rustand foreign matter. For this purpose, a protective film compatible withthe enamel material or frits is used. -Such a film may be sodiumcarbonate, borax, lithium borate, or a combination thereof, or sodiumcyanide, or nickel salts.

The borate, and particularly borax, whether from the original coatingused during forming or from a subsequent step, such as rust proofing, ishighly beneficial in limited quantity to'the subsequent enamellingoperation as it acts as a flux for the enamelling material. Therefore,extreme care in washing after forming is not essential.

Thus, in accordance with the present process, the cavities or valleysbetween the teeth or pro-' jections of the material are filled with asubstance having sufficient body to reinforce the teeth and preventtheir reduction and distortion during rolling, drawing and the like; thepores are filled and prevented from clogging with material which isdifiicult to remove; the material which operates in this manner isreadily applied and-is as easily removed and any slight amount left onthe article is beneficial in the enamelling operation.

It has been found that the present method, in addition to beingapplicable with various steels and alloy stocks of heavy tooth and highporosity such as commonly used for vitreous enamelled articles, isapplicable to ordinary carbon steels. Its applicability to ordinarycarbon steel results from two factors. First, the pickling steps. ofprior methods, when applied to ordinary carbon steels, bring the carbonof the steel to the surface and render the surface unsuitable forenamelling. Furthermore, the tooth and porosity of the original ordinarycarbon steel is limited. and is further reduced during drawing andfabricating in accordance with prior practices. Since the pickling stepis eliminated and the mechanical reduction of the tooth is prevented bythe present.

method, ordinary carbon steels can be enamelled in accordance herewith.This is particularly true of ordinary carbon steels which have been dullrolled.

Indirect advantages result from the practice of the above process, inthat the number of rejects is reduced from a relatively high percentageof processed pieces to a negligible amount, the die life is increasedindefinitely, and the down time for die touch-up, repair, jamming andthe like is eliminated.

Having described the composition to be employed in my new process ittherefore becomes convenient to list a few illustrative examples of suchcompositions, the percentages given being by weight:

Example 1 g Parts Tallow soap 15 Borax i 8 Example 2 Palm oil soap isBorax 82 I Example 3 Tallow soap 1 24 Borax 75 Borax 85 v Example 16Tallow soap 5 Polyethylene glycol 10 Borax 85 Example 17 Palm oil soap10 Polyethylene glycol 12 Borax 7'8 Example 18 Tallow soap Palm oil soap10 Polyethylene glycol 0 Polyethylene glycol oleate 1 Lithium borate 80Example 19 Cocoa butter soap 30 Polyethylene glycol oleate 5 6 l Example4 Parts Tallow soap 10 Palm oil soap 6 Borax 84 Example 5 Palm oil soap20 Borax Example 6 1 Polyethylene glycol 15 Borax Example 7 Polyethyleneglycol 22 Borax l=- 78 Example 8 Polyethylene glycol 20 Polyethyleneglycol oleate Borax 80 Example 9 I Polyethylene glycol oleate '7 Lithiumborate 93.

Example 10 Polyethylene glycol 28 Potassium borate 72 Example 11Glyceryl monostearate 12 Polyethylene glycol oleate f v Potassium borate88 Example 12 Propylene glycol stearate; '30 Lithium borate 7O Example13 Diglycol stearate 18 Borax 82 Example 14 Propylene glycol stearate 20do Glycol stearate f- Lithium borate '80 Example 15 Polyethylene glycolstearate Propylene glycol stearate Lithium borate 65 V s. Example 20Parts Stearie acid soap 5 Polyethylene glycol 30 Potassium borateEwample zl Borneo tallow' soap LL; 20 Glyceryl monostearate' 5Polyethylene glycol oleate f"? Potassium borate} i,

Borax Example 22 Hydrogenated tallow soap 'l Propylene glycol stearate25 Lithium borate 70 Example 23 Coaceric Y '1 Japanic Diglycol stearateg r 8 Propylene glycol stearate f Lithium borate} Borax Example 24Palmitic acid soap 15 Diglycol stearate 5 Borax Example 25 V Stearinflux soap 20 Borax 80 Example 26 Hydrogenated tallow soap 35 Borax 65Example 27 Hydrogenated palm oil soap lo Lithium borate 90 Example 28Triple-pressed tallow soap I 30 Hydrogenated palm oil soap Potassiumborate 79 Example 29 7 Cocoa butter soap lS Potassium borate 82 Example30 Stearin flux soap l5 Lithium borate Example 31 Coaceric soap 25 Borax'75 Example 32 V Japanic soap o 22 Potassium borate} 78 Borax Eazample33 Borneo tallow soap 20 Borax 8o Lithium borate Example 34 I Stearateacid soap 428 Borax 72 A 8' Example35 V l v Parts Stearin flux soap :7 IV 15 Steario acid soap Borax 85 Lithium borate f" "*T'f Example 36Borneo tallow soap 20 Triple-pressed palm oil soap Borax 80 Example 37Stearin flux soap l7 Borax l v Sulphonated castor oil 3 7 Example 38Hydrogenated tallow soap 22 Borax 73 Lithium borate Liquid glycol 5Sodium 'lauryl sulphate ""7 Qther modes of applying the principle of theinvention may be employed; change being made as regards the detailsdescribed, provided the features stated in any of the following claimsor the equivalent of such be employed.

This application is a continuation-in-part of my copending application,Serial No. 690,833, filed August 15, 1946 and now abandoned.

I therefore particularly point out and distinctly claim as my invention:

1. The method of producing vitreous enamelled metal articles. comprisingcoating heavy tooth porous metal stockto a thickness sumcient to coatthe peaks of the teeth of the stock and substantially fill the valleysbetween the teeth with a water-soluble, homogeneous, self-adherent'andtenacious dry lubricating and protective reinforcing coating havingsufficient body resistance to compression to reinforce and preventsubstantial deformation of the teeth of the stock during coldpressureforming thereof between two metallic dies, cold pressure formingthe coated stock into the desiredshape between two metallic dies in theabsence of any additional lubricants, Washing oil" in an aqueous bath atleast a major portion of the coating material remaining after theshaping operation, drying the shaped stock, whereby the teeth andporosity of the stock are preserved, and subsequently, in the absence ofany pickling operation suificient to cause substantial change in theshape of the teeth of the stock, vitreous enamelling the shaped stockdirectly on the formed surface while its tooth and porosity aresubstantially in the condi tion in which they existed at the completionof the washing step. i V V 2 The method according to claim 1characterized inthat said composition comprises essentially organiclubricating and binding material and a larger portion of inorganic glassforming and water liberating material.

3; The method according to claim 2 characterized in that said organiclubricating and binding material is soap and the inorganic glass formingand water liberating material is borax.

4. The method of producing vitreous enamel metal stock articlescomprising coating heavy tooth metal stock to a thickness sufficient tocoat the peaks of the teeth of the stock and substantially fill thevalleys between the teeth with a J water-soluble, homogeneous, dry,lubricating and protecting coating comprising the following ingredientsby weight:

Per cent W ater-soluble organic lubricating binder about 10-33Water-soluble alkali metal borate do 90-67 cold pressure shaping thecoated stock to theform desired between two metallic dies in the absenceof any additional lubricant, washing 011 in an aqueous bath at least asubstantial portion of the coating material remaining after the shapingoperation, drying the shaped stock, whereby the teeth and porosity ofthe stock are preserved, and subsequently, in the absence of anypickling operation suflicient to cause substantial change in the shapeof the teeth of the stock, vitreous enamelling the shaped stock whileits surface is in substantially the condition in which it existed at thecompletion of the washing step.

5. A method in accordance with claim 4 wherein in the washing operationafter the coated stock has been shaped, a portion of the lubricating andprotective coating is permitted to remain on the shaped article tofunction as a flux during the vitreous enamelling operation.

6. A method in accordance with claim 4 wherein the lubricating andprotective coating comprises the following ingredients by weight:

Per cent Water-soluble soaps about 10-33 Water-soluble borate do 90-67Per cent Water-soluble soap about 10-33 Borax do 90-67 11. A method inaccordance with claim 4 wherein the lubricating and protecting coatingcomprises:

Per cent Starch 1-8 Water-soluble soap 15-25 Borax 67-84 12. The methodof producing vitreous enamelled articles comprising coating heavy toothporous vitreous enamel metal stock to a thickness sufilcient to coat thepeaks of the teeth of the stock and substantially fill the valleysbetween the teeth with a water-soluble, homogeneous,

self-adherent and tenacious dry lubricating and protective reinforcingcoating of organic lubricant and binder comprising essentially at leastone from the group consisting of water-soluble soap, water-solublealiphatic polyhydric alcohols having less than four hydroxy groups,fatty acid esters of said alcohols, and any mixtures of any of theforegoing, and a larger portion of inorganic water-soluble glass formingand water liberating material, cold pressure forming the stock into thedesired shape between two metallic dies in the absence of any additionallubricants, washing oif in an aqueous bath at least a major portion ofthe coating material remaining after the shaping operation, drying theshaped stock, whereby the teeth and porosity of the stock are preservedin condition for vitreous enamelling, and subsequently, in the absenceof any pickling operation sufiicient to cause substantial change in theshape of the teeth of the stock, vitreous enamelling the shaped stockdirectly on the formed surface while its teeth and porosity aresubstantially in the condition in which they existed at the completionof the washing operation.

13. The method according toclaim 12 characterized in that the stock issubjected to a' light pickling operation operative to superficiallyroughen the surface of the stock without substantially afiecting theshape of the teeth, as they existed after the forming operation, priorto vitreous enamelling.

14. The method of producing articles to be vitreous enamelled from heavytoothed porous vitreous enamel stock comprising coating heavy toothedporous vitreous enamel stock to a thickness sufficient to coat the peaksof the teeth of the stock and substantially fill the valleys between theteeth with a water soluble, homogeneous, self-adherent and tenacious drylubricating and protective coating having sufiicient body resistance tocompression to reinforce and prevent substantial deformation of theteeth of the stock during cold pressure forming thereof between twometallic dies, cold pressure forming the coated stock into the desiredshape between two metallic dies in the absence of any additionallubricants, washing off in an aqueous bath at leasta major portion ofthe coating material remaining after the shaping operation and thendrying the stock, whereby the tooth and porosity of the stock arepreserved and subsequent pickling for restoring the teeth isunnecessary.

ROLAND A. WHIT'BECK.

REFERENCES CITED The following references are of record in the file ofthis patent:

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